Add new key:value pairs to existing an existing array

Question

Here's my existing data:

var nodes = [
    {i: 0, radius: 18.637872483796723},
    {i: 0, radius: 17.174333481950903},
    {i: 0, radius: 13.194447610161163},
    {i: 1, radius: 8.000718059188364},
    {i: 1, radius: 4.08204211857112}
  ];

I need to add one new key:value pairs for each item in the list. It is dynamically calculated:

cx: i*2

So the new array would look like this:

[
  {i: 0, radius: 18.637872483796723, cx: 0},
  {i: 0, radius: 17.174333481950903, cx: 0},
  {i: 0, radius: 13.194447610161163, cx: 0},
  {i: 1, radius: 8.000718059188364, cx: 2},
  {i: 1, radius: 4.08204211857112, cx: 2}
];

I am a beginner, so excuse any terminology that I've butchered (I'm not sure if I'm using the term array correctly).

Answer 1

nodes.forEach(function(n) {n.cx = n.i * 2});

Answer 2

for(var i=0; i<nodes.lenght;i++)
    nodes[i].cx = i*2;